High density polyethylene (HDPE), which spans a density range from 0.940 to 0.958 gram per cubic centimeter, finds application in injection molding, rotational molding, sheet, tubing, hose, and, of particular interest here, pipe, blow molding and geomembranes.
To be competitive, HDPE products for pipe, blow molding and geomembranes should exhibit high resistance to slow crack growth in order to prevent or significantly delay the occurrence of brittle failures under stress. At present, one of the emerging, more widely used testing methodologies for assessing slow crack growth resistance, particularly for pipe, is the Pennsylvania Notch Tensile (PENT) test. The PENT test was developed in an effort to simulate the slow crack growth resistance of a resin or fabricated pipe in an accelerated manner. The PENT test has been approved as ASTM-F 1473 and is widely used in the pipe industry as a quality control 1 quality assurance tool for the production of pressure rated pipe. Further, the HDPE should have consistently good extrusion processability.
Industry is continuously striving to find HDPE's, which, are easily processed, and, in product form, have extended PENT life.